Improved process of copying writings, maps



.producing a chemical action UNITED STATES PATENT QFFICEQ JOHN UNDERwooD, or LONDON, ENGLAND, ASSIGNOR To WALDO MAYNARD AND CHARLES R. THAYER, or BOSTON, MASSACHUSETTS.

IMPROVED PROCESS OF COPYiNG'WRlTINGS, M APS. 80C;

Specification forming part of Letters Patent No: 38,086, dated March 31, 1863.

' To all whom it may concern:

Be it known that 1, JOHN UNDERWOOD, of

London, England, have invented an improved method of printing and of preparing materials employed therein; and I do hereby declare the same to be fully described in the following specification.

The object of my invention is to facilitate the printing or production of copies of printed,

written, or other characters or marks which have been impressed or-otherwise produced upon the surface of paper, parchment, or other similar ma'teria1,'and I eifect this by preparing the substanee'of which the printed, written, or other characters or marks are composed, and also the paper, parchment, or other material upon which they are to be copied, in such manner that when the latter, after having been moistened, is brought in contact with the former a chemical action shall take place, by

I means of which copies of the printed, written,

or other characters or marks shall be produced upon the prepared paper, parchment, or other material.

In carrying my invention into effect I print,

write, or otherwise mark upon paper (supposing paper to be the material used) with a solution of an extract of logwood, or with a material or varnish soluble in water or other like suitable vehicle, and when with the latter I dust or throwover it extract of logwood in powder, and I treat the paper (supposing paper to be the material used for this purpose also) upon which the impressions are to be obtained with a solution of neutral chromate of potash or other agent which ,will have a like effect by precipitating a colored material, where the extract or powder of logwood is absorbed, and use thepaper so treated in a damp state, the impression being taken in any suitable manner.

I do not confine myself to the use of logwood and chromate of potash, orto chemical agents analogous to theirs, as the chemical agents employed to produce the desired efi'ects may be greatly varied, and the nature of the chemical action produced depends upon the agents employed. I sometimes, for example, prepare the copyingpaper with a chemical substance which shall produce the copy when in a dampstate. It

is brought in contact with the printed, writ-- a solution of oxalic acid and the characters or marks with Prussian blue freshly prepared; or I prepare the copying-paper with a chemical substance which shall produce the copy when brought into contact with the characters or marks by chemical precipitation, which is the case if I prepare the copying-paper with a solution of gallic acid and the characters or marks with a solution of sulphate of iron; or I prepare the copying-paper with a chemical substance which shall produce the copy when brought in contact with the characters or marks by chemical reaction, which is the case if I prepare the copying-paper with a solution of perchloride of iron and thecharacters or marks with a solution of sulpho-cyanide of potassium;

but while the means employed for producing the desired effects may be varied, I prefer the following for general use: I dampen the paper, parchment, .or other material which I desire to copy upon with a solution of two hundred grains of the yellow or neutral chromate of potash dissolved in one gallon of distilled water, and either use it immediately or dry it, and subsequently dampen it with water, as it is required for use. I then prepare the material which I use for producing the characters or marks, and which may be called copyingink, by simply dissolving (in a water-bath) pure extract of logwood in distilled water;'or

for printing, I use a Varnish or other similar material soluble in water, and dust or throw over it powdered extract of logwood. If' I desire to take twenty copies from an original,

-I use about six pounds of the pure extract of logwood to a gallon'of distilled water; but a larger number of copiesmaybetaken by dusting or throwing over the original before the ink has thoroughly dried a powder composed of five parts of powdered extract of logwood, one part of powdered gum-arabic, and one part of powdered tragacanth. When I desire to print from an original, in producing which I have used ink prepared as before described, I proceed by dampening six sheets of paper, prepared as before described, and having taken 01f all superfluous moisture with good blottingpaper, I place the original upon the upper sheet and press the whole for about a half a minute in a copying-press. I next remove the original, and in its place put six other sheetsof the prepared paper in a damp state, and subject the whole to pressure for about a quarter of an hour. I then take five other prepared sheets in a damp state, and, having laid the originalupon them, press them together for about two minutes, then replace the origi nal by three other prepared and damped sheets, and press the whole together for about a quarter of an hour. The extract of logwood so acts upon the neutral chromate of potash that I thus obtain twenty good clear facsimiles of the original matter or design.

This invention is applicable to the production of copies of maps, charts, plans, and other similar prints or drawings, as well as to ordinary written and printed papers or designs.

Having now described the nature of my said invention and in what manner the same is to be performed, I declare that I claim- 1. The method of printing or obtaining copies of documents, forms, maps, plans, de-

signs, or any other characters or marks which may be produced upon paper, parchment, or

other similar material, by forming these char- JOHN UNDERVVOOD.

Vitnesses;

\VILLIA STEERS, GEORGE HAZELL. 

